I randomly found a 1.16.5 bug related to water. I found this bug when I filled a certain area with water. I was hastily filling, missed and poured water in the wrong place. And it turns out that the water pours to the top, violating the laws of physics and where I poured the water does not spread. If you put a block next to this water, then nothing will change, as well as blocking the stream. If there are errors in the test, then I'm sorry, I'm writing from a translator.